1. Field of the Invention
The present invention relates to assembly of a semiconductor package, and more particularly, to a tape having implantable conductive lands which is substituted for a rigid substrate during processes for manufacturing a semiconductor package such as a ball grid array (BGA) type package, and a method for manufacturing the same.
2. Description of the Related Art
Recently, electronic products such as personal computers, cellular phones and camcorders become smaller in size and larger in processing capacity. Accordingly, a semiconductor package which is small in size, large in capacity and compliant with a fast processing speed is fully required. Therefore, semiconductor packages have been transformed from an insertional mounting type including a dual in-line (DIP) package into a surface mounting type including a thin small out-line package (TSOP), a thin quad flat package (TQFP) and a ball grid array (BGA).
The BGA, among the surface mounting types, has attracted considerable attention since it allows the size and the weight of a semiconductor package to be greatly reduced and relatively high quality and reliability to be achieved among chip scale packages (CSPs).
Recently, most semiconductor manufacturing companies have developed CSPs and published developed CSPs by unique names. However, the structures of the CSPs are very similar to one another. A BGA type package is a sort of CSP. Every conventional BGA package uses a rigid substrate formed of, for example, polyimide, bismaleimide triazine (BT) resin or FR-4, instead of using a lead frames, as the body of a semiconductor package. Here, the FR-4 is a resin produced by hardening polymer referred to as dicyandiamide, generated as an intermediate of a melamine compound.
In the rigid substrate, circuit patterns are organically patterned on the front and rear surfaces of an insulation substrate such as polyimide. The circuit patterns are firmly stuck to the insulation substrate with a phenol-based two-side adhesive having an excellent adhesive strength, or a polyimide-based one-side adhesive. The rigid substrate has via-holes formed by piercing the insulation substrate for the interconnection between the circuit patterns, and also includes a solder mask formed of an insulation material for facilitating wire bonding, attachment of external connecting terminals and protection from external damage. Typical BGA packages use solder balls or solder bumps as external connecting terminals, instead of using leads.
Such a rigid substrate remains within a semiconductor package as a part thereof after completion of assembly of the semiconductor package, so it is an obstacle in minimizing the thickness of the semiconductor package. Once in a while, a rigid substrate is eliminated in assembling an improved semiconductor package among the CSPs. However, this case has many difficulties in performing wire bonding, encapsulation and attachment of external connecting terminals.
FIG. 1 is a sectional view of a typical BGA package using a rigid substrate instead of a lead frame. The structure of a conventional BGA package will be described focusing on the manufacturing processes thereof.
Referring to FIG. 1, a wafer is cut into individual chips in a sawing process, and thus a chip 2 is prepared for a BGA package. The chip 2 is bonded to a rigid substrate 10 with an epoxy 4 in a die attach process. Bond pads (not shown) of the chip 2 are connected to bond fingers on the rigid substrate 10 through gold wires 6 in a wire bonding process.
Here, circuit patterns 12 are organically formed on the rigid substrate 10. The circuit patterns 12 formed on the front surface of the rigid substrate 10 are connected to circuit patterns such as solder ball pads 20 formed on the rear surface of the rigid substrate 10 through via-holes 16. Solder masks 14 and 14xe2x80x2 for protecting the circuit patterns 12 and for facilitating the attachment of solder balls, i.e., external connecting terminals, are formed on the front and rear surfaces, respectively, of the rigid substrate 10. An insulation substrate 18 constituting the inner portion of the rigid substrate 10 is formed of a BT resin or a plastic resin such as polyimide.
Subsequently, encapsulation for protecting the chip 2 and gold wires 6 provided on the front surface of the rigid substrate 10 is performed using an epoxy mold compound 8. Then, solder balls 22 which are external connecting terminals are attached to the solder pads 20 on the bottom of the rigid substrate 10. Finally, a strip of BGA packages is cut into individual BGA packages in a singluation process.
However, the rigid substrate used in a semiconductor packaging process according to the conventional technology has the following problems.
Firstly, intermediate connectors such as the circuit patterns 12 and 20 formed on the top and bottom of the rigid substrate 10 and via-holes 16 provided between the chip 2 and the external connecting terminals 22 degrade the electrical performance of a BGA package.
Secondarily, the insulation substrate 18 constituting the rigid substrate 10 remains within a BGA package after the completion of assembly of the BGA package, which limits the reduction of the thickness of a semiconductor package. In other words, there is a limitation in reducing the thickness of a semiconductor package.
Thirdly, since a process for forming the solder masks 14 and 14xe2x80x2 is required to ensure the insulation between the circuit patterns 12, the manufacturing is complicated.
Finally, the rigid substrate 10 is very elaborate, so it is very difficult to manufacture it and its price is very high. Therefore, the cost for assembling a BGA package is high.
To solve the above problems, it is an object of the present invention to provide a tape having implantable conductive lands, which can be used instead of a rigid substrate during a semiconductor packaging process and does not remain within a semiconductor package after the assembly of the semiconductor package.
It is another object of the present invention to provide a method for manufacturing the tape having implantable conductive lands for a semiconductor packaging process.
Accordingly, to achieve the first object of the invention, there is provided a tape for a semiconductor packaging process, including a tape film which can be detached from a semiconductor package after an encapsulation process and serves as a lead frame or a substrate until the encapsulation process is completed, in manufacturing the semiconductor package; and implantable conductive lands adhering to the tape film and each having a first surface and a second surface facing each other, wherein the first surface is attached to the tape film and connected to an external connecting terminal of the semiconductor package, and the second surface adheres to an epoxy mold compound, and wire bonding is performed on the second surface.
The tape film includes a tape body in a lower portion and an adhesive layer formed on the tape body. A surface treatment layer is preferably formed on the second surface of each implantable conductive land.
The tape film is formed of a material which does not chemically react with other materials and is not transformed by heat and pressure during the manufacture of the semiconductor package. The tape film may be formed of polymer, paper, metal or a compound including at least one of them.
The adhesive layer may be formed of an adhesive such as a silicone-resin based adhesive facilitating detachment of the tape film from the implantable conductive lands.
The implantable conductive lands are preferably formed of copper or an alloy including copper, and the preferred surface treatment layer is a material layer allowing wire bonding.
To achieve the second object of the invention, there is provided a method for manufacturing a tape having implantable conductive lands for a semiconductor packaging process. The method includes the steps of preparing a tape film serving as a lead frame or a substrate until an encapsulation process is completed, the tape film not being contained within a semiconductor package; and forming the implantable conductive lands on the tape film.
The tape film includes a tape body and an adhesive layer, and the adhesive layer is formed of silicone resin-based paste.
In one embodiment, the step of forming the implantable conductive lands includes the sub-steps of laminating a copper foil on the tape film, forming a first photo mask pattern on the copper foil, performing surface treatment for wire bonding on opening areas of the first photo mask pattern, removing the first photo mask pattern and forming a second photo mask pattern, and performing an etching process using the second photo mask pattern so that only the implantable conductive lands can remain on the tape film.
In another embodiment, the step of forming the implantable conductive lands includes the sub-steps of printing the implantable conductive lands on the tape film, and performing surface treatment for wire bonding on the printed implantable conductive lands.
In still another embodiment, the step of forming the implantable conductive lands includes the sub-steps of picking and placing the implantable conductive lands that are made in the outside on the tape film in advance, and laminating the tape film and the implantable conductive lands.
In yet another embodiment, the step of forming the implantable conductive lands includes the steps of depositing a material layer for the implantable conductive lands on the tape film, and patterning the material layer.
In still yet another embodiment, the step of forming the implantable conductive lands includes the sub-steps of forming seed layers for the implantable conductive lands on the tape film, and performing electroplating using the seed layers.
According to the present invention, a tape having implantable conductive lands is used instead of using a rigid substrate, thereby improving the electrical performance of a semiconductor package and reducing the thickness of the semiconductor package. Since the expensive rigid substrate is not used, the manufacturing cost can be reduced, and easy and simplified manufacturing can be realized. Since the path of heat radiation is shortened, the heat conducting characteristics can be improved. Since an electric circuit can be kept short, the electrical characteristics can be improved. Also, a stress problem caused by different thermal expansive coefficients of a rigid substrate and the other parts in a semiconductor package can be restrained.